1. Field
Exemplary embodiments of the present invention relate to a semiconductor design technology and, more particularly, to a semiconductor device which performs a refresh operation, and a method for driving the same.
2. Description of the Related Art
With the increase in integration of memories such as dynamic random access memory (DRAM), the space between word lines included therein has been reduced. With the reduction of space between word lines, the coupling effect between adjacent word lines has increased. Whenever data is written or read, a word line toggles between an active state and an inactive state. As the coupling effect between adjacent word lines increases, data of memory cells coupled to word lines adjacent to frequently activated word lines may be corrupted. This phenomenon is referred to as word line disturbance. Word line disturbance may cause data stored in memory cells to be lost before the memory cells are refreshed.
In order to alleviate this problem, a smart refresh technology has emerged. The smart refresh technology detects a target word line, which has been frequently activated, and refreshes memory cells coupled to word lines adjacent to the target word line. The smart refresh technology includes an additional refresh operation which is performed separately from the normal refresh operations, e.g., the auto-refresh operations.
However, when a semiconductor device operates as described above, the following issue may occur.
Refresh time, e.g., tRFC, which is a functional of the semiconductor device's design is defined in its specification. When the memory capacity of a semiconductor device increases, a refresh operation may not be completed within limited refresh time, e.g., tRFC. In other words, as the memory capacity increases, the margin of the refresh time, e.g., tRFC, decreases. Therefore, when the memory capacity of semiconductor devices is increased, a technology for securing the margin of the limited refresh time, e.g., tRFC, is required.